Power assisted steering gear



Nov. 14, 1944. A. o. ROBBINS POWER ASSISTED STEERING GEAR Filed Sept.15, 1943 2 Sheets-Sheet l INVENTOR.

m m; 11M W,

ATTORNEYS.

Nov. 14, 1944.

A. D, ROBBINS 2,362,930

POWER ASSISTED STEERING GEAR Filed Sept. 15, 1945 2 Sheets-Sheet 2 36' IF [G030 l if y I 3 41 fl a3- as l INVENTORQ 4200.2 Razz/Ms ATTORNEYS.

BY Ho wj, nm '&

, Patented Nov. 14, 1944 UNITED STATES PATENT OFFICE 2.362.930 POWERASSISTED STEERING GEAR Azor D. Robbins, GlenCove, N: 1., assignor toMack Manufacturing Corporation, Long Island City, N. Y., a corporationof Delaware Application September 15, 1943, Serial No. 502,421

4 Claims. '(01.

.trol is most valuable, that 'is, between the worm The present inventionrelates to steering mechanisms and embodies, more specifically, animproved steering mechanism by means of which the manual operation ofthe mechanism maybe assisted by a suitablepower-operated device vundercertain conditions.

The invention relates more particularly to steering mechanisms suitableespecially for use on vehicles where the steering forces are such as tomake it of considerable advantage to have available power-operatedmechanism to assist in the manual operation of the steering mechanismwhen the required steering forces reach a predetermined amount,

Numerous power-operated steering mechanisms have heretofore beendesigned in which movement of the steering column;

Th e se previously designed mechanisms, while fluid or otherpower-operated means is utilized furnishing auxiliary power toaccomplish the steering, have had certain objectionable characteristics,and an object of the present invention is to provide a steeringmechanism in which means is provided for assisting the steeringoperation by a power operated device, such powerassisting mechanismbeing brought into play by movement of the steering wheel and columnunder certain conditions.

A further object of the invention is to protrol assembly elements ofFig. 1;

lac-79.2)

and steering wheel.

vention is described in connection with the accompanying drawings,wherein Fig. 1 is a view in side elevation showing a steering mechanismconstructed in accordance with the present invention, the viewillustrating certain parts of the steering mechanism in section tofacilitate the study thereof;

Fig. 2 is a perspective view, partly brokenaway and in section, showingthe structure of the con- Fig. 3 isa view in section of shown in Fig. 1;

Fig. 4 is a view in section taken on the line 4-4 of Fig. 3 and lookingin the direction of the arows; and I Fig. 5 is a View in section takenon line 5-5 of Fig. 3 and looking in the direction of the arrows.

Referring to the above drawings, the steering wheel is shown at in asoperating a worm ll through a worm shaft l2 and l2a. Theworm II ismounted directly on the shaft section l2a which is joumalled at Ila in asuitable worm videa steering mechanism of the above character in whichthe steering shaft does not partake- .of any axial movement, its motionbeing limited entirely-to turning movement. I

Yet another object of the invention is to provide a steering mechanismof the above character wherein. normal) manual operation is insured inthe'event ofmechanical failure of the powerassisting mechanism. 7

Yet another object of the invention is to pro-' vide a steeringmechanism of the above character wherein the steering mechanism isself-returning, thus to cause the vehicle to tend to straightenout whenthe steering wheel isfreed after aturning operation. v I A further.object of the invention is to provide a steering mechanism of the abovecharacter wherein a steering gear is built as a unitary assembly and insuch fashion that it .may be conveniently assembled and serviced.

In connection with the foregoing objects and advantages, it will beobserved that the invention provides a mechanism by means of which thesteering control is located at a point where con-v and sector housinglib, The upper end of the shaft section |2a is journalled at No and hasa jaw' block 26 secured thereto, thedetails of the block being describedhereinafter.

The lower end of the shaft section I2 is provided with a jaw block 21mating with the jaw "block 26 and forming apart of a control assemblyillustrated generally at [3.

Within the housing ill) a worm sector I4 is provided, the sector beingmounted upon a crossshaft l5 having a steering arm l6 connected thereto.A control valve is provided .on the housing I lb, the valve beingillustrated generally at II in Fig. 1, fluid under pressure beingsupplied to the valve from a pump I8, Fluid pipes l9 and 20 supply fluidto either end of a cylinder 2| within which a piston 24 is provided. Thecylinder 2| and piston 24 thus provide fluid chambers 22 and 23 withwhich the respective pipes 20 and I8 communicate. I

The piston 24 is connected to a rod and rack 25 which engages with teeth25aformed 0n the sector I4, thus enabling the sector M to be op-Referring to Fig. 2, the control assembly is shown as being formed of asleeve 30 having a peripheral groove 30a within which the fingers thecontrol valve of the sleeve 30 in either direction, as indicated by thearrows in Fig. 2, will cause appropriate axial movement of the yoke 43,and thus axial movement of the sleeve is accomplished by the controlassembly, depending upon the amount of turning force required toaccomplish the steering motion. For example, the jaw block 26 is formedwith an axially extending plate 261; which is received between the jaws21a of the'jawblock 21. Springs 28 and 29 are mounted between the jaws26a and 21a to transmit the turning force of the shaft l2 to the shaftsection |2a.

Bell crank levers 3| are pivoted at 3|a in the jaw block 26 and at 3|bin the jaws 21a and are provided with arms 3|c which extend into agroove 30b, formed on the inner periphery of the sleeve 30. I

From the foregoing it will be seen that the control assembly |3 providesa means by which steering forces may be transmitted directly from Y theleft, as viewed in Fig. 3, the passage to the the shaft |2 to the shaftsection |2a through thesprings, 28 and 29 and the jaw members 26 and 21.If the steering forces are sufliciently great, either of the springs 28or 28 will becompressed, causing relative turning movement between thejaws 26a and 210., thus causing pivotal movement of the bell cranklevers.3| and a corresponding axial movement of the fingers 3|a. Thiswill cause the sleeve 30 to be moved axially in the appropriatedirection, transmitting. such axial forces to the yoke Ila. By suitablyselecting the springs 28 and 29, the extent of axial movement of thesleeve 38may be controlled as desired. In this fashion a certain desiredrange of turning forces may be secured, within which range the steeringoperations will be accomplished entirely manually. Beyond this range offorces, the power-assisting mechanism to be described previously will bebrought into play.

The power-assisting mechanism previously referred to and including therack and piston 24 is controlled-by means of a control valve H which isillustrated in greater detail in Figs. 3 and 4. The control valve willbe seen to include a' valve casing 32 having a valve sleeve 33 anda'valve 34. ,A valve head or plate 35 is provided to supply a fluidunder pressure to the valve mechanism and to deliver the controlledfluid to the pipes 9 and 2D. Fluid under pressure is supplied froma pipe36 to a port 31 and communicates with the center valve chamber 38.

The valve 34 is also formed to provide a valve chamber 46. A pipe 44serves as a return to carry the-fluid back to the source of pressure.

In Fig. .3 the valve 34 is'shown as being in a neutral position, atwhich time the pressure of the fluid at the pipe 36 and port 3'! isdistributed evenly to the openings 39, 4|), 4|, and 42 formed in thevalve casing. In this position of the valve, fluid under pressure entersfrom port 31 into the chamber 38 and flows equally into ports 4| and 42and also into ports 39 and 40. Free passage of the fluid is thuspermitted with the valve 34 in the position shown in Fig. 3 and thepower-assisting mechanism remains dormant.

The mechanism comes into play upon the application of sufiicientresistance tothe turning of shaft I2, this resistance being set up bythe shaftsection |2a and related steering elements. Upon such resistancecoming into existence, the jaw member 26 will oppose the free motion ofthe control-assembly shown in Fig. 2 and there will be a relativerotation between the jaw members 2 6 and 21 which will set upacorresponding duct 4| becomes larger and the passage to the duct 43correspondingly smaller. ously, the passage to the valve chamber 46 fromthe port 42 becomes larger,- permitting easier scavenging of thefluid inthe inactive side of the power cylinder. Also, with the enlargement ofthe passage between the ports 31 and 4|, the

passage to the port'39 becomes smaller. In this fashion most of thefluid under pressure is supplied to the duct 4| and thus to the powercylinder 2| through the pipe 20. This fluid enters the chamber 22 and isapplied to the upper side of the piston 24, thus causing the rack 25 toprovide assisting power to the sector |4 through the teeth 25a. Thefluid in chamber 23 is forced out through the pipe |9, port 42, valvechamber 46, and port 40 to the return pipe 44.

Relative movement between the shaft l2 and shaft section |2a in theopposite direction causes a reversal of movement of the valve 34 and acor- .28 and 28 are properly selected. When this is done, the bellcranklevers are not moved pivotally and the control sleeve is notshifted axially so that there is no valve motion and no power assistance.to the steering operation. As soon as the resistance to steeringincreases sufliciently, the springs yield and there is a relative motionbetween the jaw members which is transmitted to the valve member 34 toprovide steering assistance.

As shown in Fig. 5, the valve plate 35 is formed with a passage 41communicating through a vault chamber 48 with a passage 48 thatcommunicates with the pipe 36. The passage 41 communicates with thereturn pipe 21 and a ball 50 is seated in the ball chamber 48 by meansof a light spring 5|. This mechanism provides a relief valve to alldw afree interchange of the power fluid between the high and low pressuresides of the system'in the event of failure of pressure from the fluidsystem. Under this condition the steering gear operates as a normalsteering gear and without any power assistance.

From the foregoing it will be seen that a steering gear has beenprovided wherein the steering gear is free to rotate but does notpartake of any axial movement. The only axially movable element is thecontrol sleeve and valve, and the steering control is placed between theworm and and assembled in operating position.

While the invention has been described in reference to the accompanyingdrawings, it is not Simultaneas defined in the appended shaft, asteering arm, a shaft section coaxial with the shaft and connected tooperate the arm, a

connection between the shaft and shaft section to permit a limitedrelative rotary motion therebetween, a bell crank lever pivoted to' theshaft and to the shaft section and movable in response to relativemovement of said shaft and said shaft section, a crank armon the lever,a sleeve connected to said crank arm and slidable axially with respectto the shaft and shaft section upon movement of said lever, and powermeans responsive to movement of the sleeve to apply power to the arm. I

Steering mechanism comprising a steering shaft, a steering arm, a shaftsection coaxial with the shaft and connected to operate the arm, aconnection between the shaft and shaft section to permit a limitedrelative rotary motion therebetween, means to resist, yieldingly, saidrelative rotary motion, a bell crank lever pivoted to the shaft and tothe shaft section, a crank arm on the lever, a sleeve slidable axiallywith respect to the shaft and shaft section, means to operate the sleeveby the crank arm, and power means responsive to movement of the sleeveto apply power to the arm.

jaw members on the shaft and shaft section, plates on the jaw members,one of said plates on one of said members extending between plates onthe other of said jaw members, springs between the plates to resist,yieldingly, relative movement therebetween, a bell crank lever piv-loted to each of said plates between relatively moving surfaces thereof,a crank arm on the bell crank member, a sleeve slidable axially on thejaw members and formed with a groove on the inner periphery thereof toreceive the crank arm, and power means responsive to movement of thesleeve to apply power tothe' arm.

4. Steering mechanism comprising a steering shaft, a, steering arm, ashaft section coaxial with the shaft and connected to operate the arm, aconnection between the shaft and shaft section to permit a limitedrelative rotary motion therebetween, a bell crank'lever pivoted to theshaft 3. Steering mechanism comprising a steering shaft, a steering arm,a shaft section coaxial with the shaft and connected to operate the arm,

first-named sleeve.

and to the shaft section, a crank arm on the lever, a sleeve. slidableaxially with respect to the shaft and shaft section, means to operatethe sleeve by the crank arm, a source of fluid under pressure, acylinder, connections between the cylinder and arm for applying power tothe 'ar'm valve means, conduits between valve means and the fluid sourceand cylinder, a valve sleeve in the valve means having portscommunicating with the conduits, a valve slidable in the valve sleeve,and means to operate the valve by the AZOR- D. ROBBINS.

